The present invention relates to a needle bearing which is used in a car air conditioner or in a planetary unit for an automatic transmission.
In a compressor for a car air conditioner or in a planetary unit for an automatic transmission, as a bearing for supporting a thrust load applied to a rotary part, there is used a thrust needle bearing. However, in the compressor for a car air conditioner, since HFC134a (Hydro Fluoro Carbon 134a) or PAG (Polyalkylene glycol) is used as a refrigerant or operating oil, the lubricating condition of the bearing is under a very severe environment. And, the rotation condition of the bearing also ranges widely from high speeds to low speeds, and further the load to be applied to the bearing ranges from a condition of almost no load to a condition of about 5000N; and, depending on the operating conditions of the compressor, these conditions are combined together at random.
Therefore, under the environment requiring such severe lubricating condition, there is required a thrust needle bearing which can provide better lubricating performance and, to satisfy such requirement, conventionally, for example, the surface roughness of a ring or a rolling body is enhanced or, as shown in FIGS. 19A and 19B, in a thrust ring 1, there are formed notches 2 which are used to secure an oil passage. Also, as shown in FIG. 20, in order to secure the passing oil amount of lubricating oil, the collar portions 4 of an outer ring 3 are turned over to thereby increase the opening height h.
However, in the compressor for a car air conditioner or in the planetary unit for an automatic transmission (A/T), originally, since the lubricating condition is very severe, the above-mentioned measures can provide little effect. Also, because the lubricating condition is very severe, for example, there occurs metal contact between the ring and rolling body. Therefore, in case where foreign substances higher in hardness than the rolling body are sticking to the raceway surface of the ring and the pocket inner surface of the retainer to be contacted with the rolling body, the rolling body is worn due to the influence of the foreign substances, thereby raising a fear that the bearing can be flaked or seized.